1. Field
The present disclosure relates generally to drilling and, in particular, to drilling through pilot holes. Still more particularly, the present disclosure relates to a method and apparatus for automating the drilling of a hole in a stackup that overlaps pilot holes through the stackup within selected tolerances.
2. Background
In some manufacturing processes, a first part may be fastened to a second part by temporarily securing the two parts together to form a stackup, drilling a hole through the stackup, and installing a fastener through the hole. As one illustrative example, a first part, such as a skin panel for an aircraft, may be positioned relative to a second part, such as a frame for the aircraft, to form a stackup. In particular, the first part may be positioned relative to the second part such that a first pilot hole in the skin panel is at least partially aligned with a second pilot hole in the frame. The skin panel may be temporarily secured to the frame by inserting a temporary fastener, such as a tack fastener, through the two pilot holes. The tack fastener may reduce or prevent relative movement between the skin panel and the frame during drilling operations.
A drill may be used to drill a hole through the two pilot holes and the tack fastener such that the drilled hole can receive a fastener. The drilled hole may need to completely overlap both the first pilot hole in the skin panel and the second pilot hole in the frame to meet manufacturing requirements. However, with some currently available drilling systems and methods, the drilled hole formed may not completely overlap both pilot holes.
One currently available drilling system may center the drill bit on the center of the exposed end of the tack fastener to position the drill and perform drilling. Positioning the drill bit of the drilling system may be equivalent to positioning the drill column for the drilling system. The drill column may be an imaginary column that represents the hole to be drilled. The drill bit may be positioned at the exposed side of the first part. In this manner, the second pilot hole in the second part may not be visible to the drill. In other words, the second pilot hole may be a “blind hole.”
When the drill column is centered on the exposed end of the tack fastener, the hole that is drilled may not completely overlap both pilot holes in both parts. For example, without limitation, the drilled hole may not completely overlap the blind hole. This type of drilled hole may be referred to as a double drilled hole because the blind hole is not completely overlapped and consumed by the drilling process. The diameter of the drilled hole through the second part may be larger than the diameter of the drilled hole through the first part. As a result, this drilled hole may not meet manufacturing requirements or be in conformance.
When a double drilled hole is formed, an operator may need to examine the double drilled hole to determine whether the parts need to be discarded or whether the hole can be made larger to completely overlap the blind hole. A larger fastener may then be installed in the larger hole. However, forming a larger hole may not always be possible given requirements for the edge margins for holes in parts.
When multiple holes are to be drilled into a stackup having tacked pilot holes, automated drilling systems may be unable to drill these holes as quickly and efficiently as desired. An operator may need to manually inspect each hole drilled by the automated system to ensure that the hole is not a double drilled hole. This process may be more time-consuming and labor-intensive than desired and may slow down manufacturing times. Further, the equipment and/or tools needed to currently avoid drilling double drilled holes may be more expensive then desired. Therefore, it would be desirable to have a method and apparatus that take into account at least some of the issues discussed above, as well as other possible issues.